Porphyromonas gingivalis-induced hematogenous disseminated severe pneumonia: a case report.

Porphyromonas gingivalis, a gram-negative oral anaerobe among more than more than 500 bacterial species that colonizing the oral cavity, is involved in the pathogenesis and prototypic polybacterial consortium of periodontitis. It is mainly found in oral infections and rarely present in other organ diseases. Here, we describe a 43-year-old man with underlying diabetes who developed hematogenous disseminated severe pneumonia after P. gingivalis had invaded the blood. Next-generation sequencing of early alveolar lavage fluid and blood samples confirmed the diagnosis. The patient's lung infection improved after targeted antimicrobial treatment. He was successfully weaned from ventilatory support and transferred to the general ward. This case illustrates bacterial entry into the bloodstream of a patient with diabetes who had periodontal disease but did not maintain oral hygiene, leading to severe pneumonia. Periodontal disease is often ignored by the public, and it is difficult for critical care physicians to link severe pneumonia with periodontal disease. Thus, this case represents an important warning to critical care clinicians.

BTNL2 promotes colitis-associated tumorigenesis in mice by regulating IL-22 production.

Interleukin 22 (IL-22) has an important role in colorectal tumorigenesis and many colorectal diseases such as inflammatory bowel disease and certain infections. However, the regulation of IL-22 production in the intestinal system is still unclear. Here, we present evidence that butyrophilin-like protein 2 (BTNL2) is required for colorectal IL-22 production, and BTNL2 knockout mice show decreased colonic tumorigenesis and more severe colitis phenotypes than control mice due to defective production of IL-22. Mechanistically, BTNL2 acts on group 3 innate lymphoid cells (ILC3s), CD4+ T cells, and γδ T cells to promote the production of IL-22. Importantly, we find that a monoclonal antibody against BTNL2 attenuates colorectal tumorigenesis in mice and that the mBTNL2-Fc recombinant protein has a therapeutic effect in a dextran sulfate sodium (DSS)-induced colitis model. This study not only identifies a regulatory mechanism of IL-22 production in the colorectal system but also provides a potential therapeutic target for the treatment of human colorectal cancer and inflammatory bowel diseases.

RNF186/EPHB2 Axis Is Essential in Regulating TNF Signaling for Colorectal Tumorigenesis in Colorectal Epithelial Cells.

The receptor tyrosine kinase EPHB2 (EPH receptor B2) is highly expressed in many human cancer types, especially in gastrointestinal cancers, such as colorectal cancer. Several coding mutations of the EPHB2 gene have been identified in many cancer types, suggesting that EPHB2 plays a critical role in carcinogenesis. However, the exact functional mechanism of EPHB2 in carcinogenesis remains unknown. In this study, we find that EPHB2 is required for TNF-induced signaling activation and proinflammatory cytokine production in colorectal epithelial cells. Mechanistically, after TNF stimulation, EPHB2 is ubiquitinated by its E3 ligase RNF186. Then, ubiquitinated EPHB2 recruits and further phosphorylates TAB2 at nine tyrosine sites, which is a critical step for the binding between TAB2 and TAK1. Due to defects in TNF signaling in RNF186-knockout colorectal epithelial cells, the phenotype of colitis-propelled colorectal cancer model in RNF186-knockout mice is significantly reduced compared with that in wild-type control mice. Moreover, we find that a genetic mutation in EPHB2 identified in a family with colorectal cancer is a gain-of-function mutation that promoted TNF signaling activation compared with wild-type EPHB2. We provide evidence that the EPHB2-RNF186-TAB2-TAK1 signaling cascade plays an essential role in TNF-mediated signal transduction in colorectal epithelial cells and the carcinogenesis of colorectal cancer, which may provide potential targets for the treatment of colorectal cancer.

DOCK2 regulates antifungal immunity by regulating RAC GTPase activity.

Fungal infections cause ~1.5 million deaths each year worldwide, and the mortality rate of disseminated candidiasis currently exceeds that of breast cancer and malaria. The major reasons for the high mortality of candidiasis are the limited number of antifungal drugs and the emergence of drug-resistant species. Therefore, a better understanding of antifungal host defense mechanisms is crucial for the development of effective preventive and therapeutic strategies. Here, we report that DOCK2 (dedicator of cytokinesis 2) promotes indispensable antifungal innate immune signaling and proinflammatory gene expression in macrophages. DOCK2-deficient macrophages exhibit decreased RAC GTPase (Rac family small GTPase) activation and ROS (reactive oxygen species) production, which in turn attenuates the killing of intracellular fungi and the activation of downstream signaling pathways. Mechanistically, after fungal stimulation, activated SYK (spleen-associated tyrosine kinase) phosphorylates DOCK2 at tyrosine 985 and 1405, which promotes the recruitment and activation of RAC GTPases and then increases ROS production and downstream signaling activation. Importantly, nanoparticle-mediated delivery of in vitro transcribed (IVT) Rac1 mRNA promotes the activity of Rac1 and helps to eliminate fungal infection in vivo. Taken together, this study not only identifies a critical role of DOCK2 in antifungal immunity via regulation of RAC GTPase activity but also provides proof of concept for the treatment of invasive fungal infections by using IVT mRNA.

Cancer cell-expressed BTNL2 facilitates tumour immune escape via engagement with IL-17A-producing γδ T cells.

Therapeutic blockade of the immune checkpoint proteins programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA4) has transformed cancer treatment. However, the overall response rate to these treatments is low, suggesting that immune checkpoint activation is not the only mechanism leading to dysfunctional anti-tumour immunity. Here we show that butyrophilin-like protein 2 (BTNL2) is a potent suppressor of the anti-tumour immune response. Antibody-mediated blockade of BTNL2 attenuates tumour progression in multiple in vivo murine tumour models, resulting in prolonged survival of tumour-bearing mice. Mechanistically, BTNL2 interacts with local γδ T cell populations to promote IL-17A production in the tumour microenvironment. Inhibition of BTNL2 reduces the number of tumour-infiltrating IL-17A-producing γδ T cells and myeloid-derived suppressor cells, while facilitating cytotoxic CD8+ T cell accumulation. Furthermore, we find high BTNL2 expression in several human tumour samples from highly prevalent cancer types, which negatively correlates with overall patient survival. Thus, our results suggest that BTNL2 is a negative regulator of anti-tumour immunity and a potential target for cancer immunotherapy.

Edible fungus slag derived nitrogen-doped hierarchical porous carbon as a high-performance adsorbent for rapid removal of organic pollutants from water.

In this work, agricultural waste edible fungus slag derived nitrogen-doped hierarchical porous carbon (EFS-NPC) was prepared by a simple carbonization and activation process. Owing to the biodegradation and infiltrability of hyphae, this EFS-NPC possessed an ultra-high specific surface area (3342 m2/g), large pore volume (1.84 cm3/g) and abundant micropores and mesopores. The obtained EFS-NPC could effectively adsorb bisphenol A (BPA) with the maximal adsorption capacity of 1249 mg/g and the removal process reached 89.9% of the equilibrium uptake in the first 0.5 h. Besides, the EFS-NPC showed much better removal performance towards 2,4-dichlorophenol (2,4-DCP) and methylene blue (MB) than commercial activated carbons (Norit RO 0.8 and DARCO granular activated carbon). Furthermore, adsorption isotherms, thermodynamics and kinetics researches indicated that the adsorption process of BPA was monolayer, exothermic and spontaneous. This research has given evidence that the low-cost EFS-NPC can serve as a high-efficient adsorbent for removing organic contaminants from water.

Coherent perfect absorption and asymmetric interferometric light-light control in graphene with resonant dielectric nanostructures.

Engineering light absorption in graphene has been the focus of intensive research in the past few years. In this paper, we show numerically that coherent perfect absorption can be realized in monolayer graphene in the near infrared range by harnessing resonances of dielectric nanostructures. The asymmetry of the structure results in different optical responses for light illuminated from the top side and the substrate side and enables asymmetric interferometric light-light control. The absorbed and scattered light exhibit interesting nonlinear behavior, allowing switching a strong optical signal output with a weak light. This work may stimulate potential applications including new types of sensors, coherent photodetectors and all-optical logical devices.

[Impact of Size on Environmental Behavior of Metal Oxide Nanoparticles].

With the rapid development of nanotechnology, the environmental behavior and ecological effect of nanoparticles (NPs) are receiving more and more attention. As an important environmental component, metal oxide NPs occur widely in nature, such as in water bodies, air, soils, and sediments. They have a large surface area and high surface activity, allowing them to control and affect the speciation, migration, transformation, and bioavailability of some contaminants and nutrients in the environment. The nano-size is a unique property of nanoparticles. The size of particles regulates and determines the structure and physicochemical properties of nano-oxides, which greatly affects interfacial reactions with the relevant elements and environmental geochemical behaviors. The effects of NPs size on the environmental geochemical behaviors, such as adsorption, (reductive) dissolution, (catalytic) oxidation, aggregation and transport, are briefly summarized, and the mechanism of the size effect is discussed. Finally, hot spots for future research of metal oxide nanoparticles related to size effects in the environment are proposed.

[Partial resection, inner thigh skin graft, and glans reconstruction for early-stage penile cancer: A report of 6 cases].

OBJECTIVE: To explore the optimal methods for the reconstruction and preservation of the glans after partial penis resection in the treatment of early-stage penile cancer. METHODS: Between January 2012 and June 2015, we treated 6 cases of early- stage penile cancer by partial penis resection, inner thigh skin graft, and glans reconstruction and followed them up for 0.5-3 years. RESULTS: The length of the penis before and after operation was ([6.5 ± 1.2] vs [4.5 ± 1.8] cm) in the flaccid state and ([12.8 ± 2.3] vs [9.1 ± 2.1] cm) in the erectile state. The sense of the reconstructed glans was completely recovered at 3 months after surgery. The glans skin was pale red and soft, nearly normal at 12 months, with no obvious graft contracture or scar formation. All the patients achieved normal erection and their partners were satisfied with their intercourse. No recurrence or metastasis was observed. CONCLUSION: The strategy of partial penis resection, inner thigh skin graft and glans reconstruction, simple, effective, and with few complications, is one of the best treatments of early-stage penile cancer, which not only ensures radical removal of the tumor but also maximally reserves the function of the organ.

Lactoferrin promote primary rat osteoblast proliferation and differentiation via up-regulation of insulin-like growth factor-1 expression.

The aim of this study was to explore the effect of lactoferrin (LF) in primary fetal rat osteoblasts proliferation and differentiation and investigate the underlying molecular mechanisms. Primary rat osteoblasts were obtained from the calvarias of neonatal rats. Osteoblasts were treated with LF (0.1-1000 µg/mL), or OSI-906 [a selective inhibitor of insulin-like growth factor 1 (IGF-1) receptor and insulin receptor]. The IGF-1 was then knocked down by small hairpin RNA (shRNA) technology and then was treated with recombinant human IGF-1 or LF. Cell proliferation and differentiation were measured by MTT assay and alkaline phosphatase (ALP) assay, respectively. The expression of IGF-1 and IGF binding protein 2 (IGFBP2) mRNA were analyzed using real-time PCR. LF promotes the proliferation and differentiation of osteoblasts in a certain range (1-100 µg/mL) in time- and dose-dependent manner. The mRNA level of IGF-1 was significantly increased, while the expression of IGFBP2 was suppressed by LF treatment. Knockdown of IGF-1 by shRNA in primary rat osteoblast dramatically decreased the abilities of proliferation and differentiation of osteoblasts and blocked the proliferation and differentiation effect of LF in osteoblasts. OSI906 (5 µM) blocked the mitogenic and differentiation of LF in osteoblasts. Proliferation and differentiation of primary rat osteoblasts in response to LF are mediated in part by stimulating of IGF-1 gene expression and alterations in the gene expression of IGFBP2.

[Sorption and desorption characteristics of different structures of organic phosphorus onto aluminum (oxyhydr) oxides].

The sorption and desorption characteristics of four kinds of organic phosphorus with different molecular structures (glycerophosphate (GP), glucose-6-phosphate (G6P), adenosine triphosphate (ATP), and myo-inositol hexakisphosphate (IHP)) on three kinds of aluminum (oxyhydr)oxides (amorphous Al(OH)3, boehmite, and alpha-Al2O3) were studied. The underlying mechanisms were also illustrated. Results showed that the maximum sorption amounts of OP onto Al (oxyhydr)oxides, on a per gram dry weight basis, decreased as following: amorphous Al(OH)3 > boehmite > alpha-Al2O3. This mainly related to the mineral crystallinity and surface heterogeneity. With the exception of sorption of IHP on amorphous Al (OH)3, the maximum sorption density decreased with increasing molecular weight (MW) of OP, following the order: GP > G6P > ATP > IHP. However, the sorption amount of IHP on amorphous Al (OH)3 was much higher than those of other OP, due to the transformation of surface complexes of IHP to surface precipitation and thus enhancing the sorption. The sorption kinetics results showed that sorption of OP underwent the first onset rapid sorption, i. e. a certain amount of sorption occurred within an onset extremely short period, and a following long and slow sorption process. Amorphous Al (OH)3 had the greatest onset rapid sorption density, and the onset rapid sorption density of OP on Al (oxyhydr) oxides decreased with increasing MW. Desorption capacities of OP by KCl and citrate solutions related to the surface affinity between OP and boehmite. Initial desorption percentages by KCl decreased in the order: G6P (10.53%) > GP(6.91%) > ATP (3.06%) > IHP (0.8%). The maximum desorption percentages of OP by citrate were 4-5 times greater than those by KCl. During resorption process of P by KCl, the maximum desorption rate achieved after a fast desorption in a few hours, followed by diffusion-resorption during which the desorption percentage gradually decreased. Specially, both diffusion-resorption and surface precipitation promoted the resorption of IHP on mineral surface. Conclusively, the strong specific sorption of OP occurs on the surface of Al (oxyhydr) oxides, and molecular structure and size of OP as well as the crystallinity and crystal structure of minerals are the key factors affecting the interfacial reactions and environmental behaviors of OP.

Thermally stable ionic liquid-based sol-gel coating for ultrasonic extraction-solid-phase microextraction-gas chromatography determination of phthalate esters in agricultural plastic films.

A novel sol-gel-coated ionic liquid-based ([AMIM][N(SO(2)CF(3))(2)]-OH-TSO) fiber was successfully applied for the determination of phthalate esters (PAEs) in agricultural plastic films by ultrasonic extraction (UE) combined with solid phase microextraction-gas chromatography (SPME-GC) due to its high thermal stability, specific selectivity and extraction efficiency. The extractant for UE and the adsorption time for SPME were optimized to achieve higher extraction efficiency. The desorption temperature and time were also optimized to avoid the carryover effect of previous extraction, and ultimately improve the precision and accuracy of the method. The [AMIM][N(SO(2)CF(3))(2)]-OH-TSO fiber showed comparable, or even higher response to most of the investigated PAEs than the commercial PDMS, PDMS-DVB and PA fibers. The carryover problem, often encountered when using commercial fibers, had been eliminated when desorption was performed at 360°C for 8 min. The proposed SPME-GC method showed good linearity over three to four orders of magnitude, and low limits of detection ranged from 0.003 to 0.063 µg L(-1). The relative standard deviation values obtained were below 10%, and the recoveries were in the ranges of 90.2-111.4%. Some of the PAEs studied were detected at very high concentration in these agricultural plastic film samples, resulting in a potential risk of crop damage, environmental contamination and human health exposure.

[Lead adsorption and arsenite oxidation by cobalt doped birnessite].

In order to study the effects of transition metal ions on the physic-chemical properties of manganese dioxides as environmental friendly materials, three-dimensional nano-microsphere cobalt-doped birnessite was synthesized by reduction of potassium permanganate by mixtures of concentrated hydrochloride and cobalt (II) chloride. Powder X-ray diffraction, chemical analysis, N2 physical adsorption, field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectra (XPS) were used to characterize the crystal structure, chemical composition and micro-morphologies of products. In the range of molar ratios from 0.05 to 0.20, birnessite was fabricated exclusively. It was observed that cobalt incorporated into the layers of birnessite and had little effect on the crystal structure and micromorpholgy, but crystallinity decreased after cobalt doping. Both chemical analysis and XPS results showed that manganese average oxidation state decreased after cobalt doping, and the percentage of Mn3+ increased. Co(III) OOH existed mainly in the structure. With the increase of cobalt, hydroxide oxygen percentage in molar increased from 12.79% for undoped birnessite to 13.05%, 17.69% and 17.79% for doped samples respectively. Adsorption capacity for lead and oxidation of arsenite of birnessite were enhanced by cobalt doping. The maximum capacity of Pb2+ adsorption increased in the order HB (2 538 mmol/kg) < CoB5 (2798 mmol/kg) < CoB10 (2932 mmol/kg) < CoB20 (3 146 mmol/kg). Oxidation percentage of arsenite in simulated waste water by undoped birnessite was 76.5%, those of doped ones increased by 2.0%, 12.8% and 18.9% respectively. Partial of Co3+ substitution for Mn4+ results in the increase of negative charge of the layer and the content of hydroxyl group, which could account for the improved adsorption capacity of Pb2+. After substitution of manganese by cobalt, oxidation capacity of arsenite by birnessite increases likely due to the higher standard redox potential of Co3+/Co2+ than those of Mn4+/Mn3+/Mn2+. Therefore, Co-doped birnessite is more applicable for the remediation of water polluted with heavy metal ions, implying new methods of modification of manganese dioxides in practice.

[Investigation on the oxidation behaviors and kinetics of sulfide by cryptomelane].

As one of the common manganese oxide minerals in supergene environment, cryptomelane affects the migration, transformation and environmental fate of sulfur in soil. In this work, oxidation process of sodium sulfide solution by cryptomelane was investigated without oxygen gas. The species and concentration of oxidation products of sulfide in solution were determined by spectrophotometry and ion chromatography, and the crystal structures and micro-morphologies of solid oxidation products of sulfide were characterized by XRD and SEM. The influence of solution temperature, pH value of solution, manganese average oxidation state (AOS) and the amount of added cryptomelane on the initial oxidation rate of S2- was studied. It was observed that the oxidation products of sulfide were S2O3(2-), SO3(2-), SO4(2-) and S, and S was the main one for that the total transformation rate of S2- to S2O3(2-), SO3(2-) and SO4(2-) was below 13.4%. The initial oxidation rate of S2- follows a pseudo-first-order law. Oxidation rate increased with elevating reaction temperature, decreasing pH value of solution and the increase of the amount of added mineral. The oxidation capacity of cryptomelane increased with the increase of Mn(III) content, and the initial oxidation rate constants (K(obs)) of S2- were 0.220 3 min(-1) and 0.1729 min(-1) when cryptomelane was applied with AOS about 3.81 and 3.98, respectively. During the redox process, cryptomelane was reduced to Mn(OH)2, which could be oxidized into Mn3O4, by O2 in air, and Mn3O4 was further transformed into MnOOH likely due to the reaction of surface-adsorbed water on manganese oxide and O2 and Mn3O4.

Preparation and characterization of novel crown ether functionalized ionic liquid-based solid-phase microextraction coatings by sol-gel technology.

A novel crown ether functionalized ionic liquid (IL), 1-allyl-3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium hexafluorophosphate was synthesized and used as selective stationary phase to prepare task-specific IL-based solid phase microextraction (SPME) fibers by sol-gel method and free radical cross-linking technology. The underlying mechanism of the sol-gel reaction was proposed and the successful chemical bonding of the crown ether functionalized IL to the formed hybrid organic-inorganic copolymer coating was confirmed by FT-IR spectroscopy. The performance of this in situ created crown ether functionalized IL-based SPME fibers, was investigated in detail. The coating has porous surface structure, stable performance in high temperature (to 340 °C) and in different solutions (water, organic solvent, acid and alkali), and good coating preparation reproducibility. In contrast to the sol-gel derived 1-allyl-3-methyl imidazolium hexafluorophosphate-based coating prepared in our previous work with the identical procedure, the extraction performance of this newly developed sol-gel crown ether functionalized IL-based coating was superior for alcohols, phthalate esters, phenolic environmental estrogens, fatty acids and aromatic amines due to the introduction of benzo-15-crown-5 functional group in IL structure. Moreover, it was shown to provide higher or comparable extraction efficiencies for most analytes studied than did the commercial PDMS, PDMS/DVB and PA fibers.

[Adsorption of heavy metals on the surface of birnessite relationship with its Mn average oxidation state and adsorption sites].

Adsorption characteristics of mineral surface for heavy metal ions are largely determined by the type and amount of surface adsorption sites. However, the effects of substructure variance in manganese oxide on the adsorption sites and adsorption characteristics remain unclear. Adsorption experiments and powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were combined to examine the adsorption characteristics of Pb2+, Cu2+, Zn2+ and Cd2+ sequestration by birnessites with different Mn average oxidation state (AOS), and the Mn AOS dependent adsorption sites and adsorption characteristics. The results show that the maximum adsorption capacity of Pb2+, Cu2+, Zn2+ and Cd2+ increased with increasing birnessite Mn AOS. The adsorption capacity followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The observations suggest that there exist two sites on the surface of birnessite, i. e., high-binding-energy site (HBE site) and low-binding-energy site (LBE site). With the increase of Mn AOS for birnessites, the amount of HBE sites for heavy metal ions adsorption remarkably increased. On the other hand, variation in the amount of LBE sites was insignificant. The amount of LBE sites is much more than those of HBE sites on the surface of birnessite with low Mn AOS. Nevertheless, both amounts on the surface of birnessite with high Mn AOS are very close to each other. Therefore, the heavy metal ions adsorption capacity on birnessite is largely determined by the amount of HBE sites. On birnessite surface, adsorption of Cu2+, Zn2+, and Cd2+ mostly occurred at HBE sites. In comparison with Zn2+ and Cd2+, more Cu2+ adsorbed on the LBW sites. Pb2+ adsorption maybe occupy at both LBE sites and HBE sites simultaneously.

[Characterization of Pb2+ adsorption on the surface of birnessite treatment with Na4P2O7 at different pH and the study on the distribution of Mn(III) in the birnessite].

Acid birnessite was treated with Na4P2O7 at pH 2, 4, 5 respectively. After the treatments, the species and content of manganese ion in the complex solution, and the variation of average oxidation state (AOS) of Mn in birnessite, and the amount of adsorbed Pb2+ and released Mn2+, H+ during the Pb2+ adsorption were investigated. The results indicate that after acid birnessite, the AOS of Mn is 3.670 which is treated by Na4P2O7 at different pH, Mn( III) located in the layer edge and part of Mn(III) located in the interlayer are released to the solution through complexation with Na4P2O7. The content of Mn(III) in the structure of original birnessite is very low. Small amount of Mn(II), which accounts for 4.70%-7.46% in the molar percentage of total released Mn, is also released simultaneously. The AOS of Mn of birnessites after treatment increases to 3.783 (pH 2), 3.786 (pH 4), 3.824 (pH 5) respectively. While the crystal structure of birnessite does not change after treatment, the amount of Mn(III) located above or below vacant cation sites decreases, and the amount of H+ located above or below vacant cation sites goes up in the structure of birnessites. The amount of vacant cation sites responsible for Pb2+ adsorption increases, which lead to the increase of the maximum amount of adsorbed Pb2+. Additionally, the distribution of Mn(III) in the structure of acid birnessite is deduced. About one sixth of Mn(III) locates in the layer edge, and five sixths of Mn(III) locates in the interlayer and the non layer edge.

Cation effects on the layer structure of biogenic Mn-oxides.

Biologically catalyzed Mn(II) oxidation produces biogenic Mn-oxides (BioMnO(x)) and may serve as one of the major formation pathways for layered Mn-oxides in soils and sediments. The structure of Mn octahedral layers in layered Mn-oxides controls its metal sequestration properties, photochemistry, oxidizing ability, and topotactic transformation to tunneled structures. This study investigates the impacts of cations (H(+), Ni(II), Na(+), and Ca(2+)) during biotic Mn(II) oxidation on the structure of Mn octahedral layers of BioMnO(x) using solution chemistry and synchrotron X-ray techniques. Results demonstrate that Mn octahedral layer symmetry and composition are sensitive to previous cations during BioMnO(x) formation. Specifically, H(+) and Ni(II) enhance vacant site formation, whereas Na(+) and Ca(2+) favor formation of Mn(III) and its ordered distribution in Mn octahedral layers. This study emphasizes the importance of the abiotic reaction between Mn(II) and BioMnO(x) and dependence of the crystal structure of BioMnO(x) on solution chemistry.

[Effects of Mn(III) on oxidation of Cr(III) with birnessites].

Cr(III) could be oxidized only by manganese oxide minerals as natural inorganic oxidants in nature, and so the rate and mechanism of interaction between manganese oxide minerals and Cr(III) were widely concerned. The effects of Mn(III) in birnessites, the most common Mn oxide mineral in the environment, on the rate of Cr(III) oxidation with birnessites and the kinetic characteristics were investigated through batch kinetic technique. The results show that Cr(III) oxidation rate follows a pseudo-first-order reaction, and the apparent rate constant K(obs), is 0.031 3 min(-1) when the average oxidation state (AOS) of Mn is about 3.50 in birnessite. When the birnessite is pretreated with Na4P2O7 solution, and the Mn(III) can be complexed out from the solid oxides. Therefore the content of Mn(III) in the birnessites decreases and the AOS of manganese increases. The AOSs of Mn for the pretreated birnessites increase from 3.50 to 3.63, 3.73 and 3.78 when the concentrations of Na4P2O7 are about 10, 20 and 50 mmol/L respectively. The Mn(III) content does not affect the initial oxidation rate of Cr(III) markedly, although oxidation amount of Cr(III) increases with the AOS of Mn. The apparent rate constants for the corresponding pretreated birnessites are 0.035 1, 0.032 5 and 0.0309 min(-1) respectively. The oxidation rate of Cr( III) is markedly influenced by the amount of Mn(III) produced in the transformation process of Mn(VN) --> Mn(III). The newly formed Mn(III) is complexed by Na4P2O7 and the oxidation rate decreases to 45%-88%. The lower content of Mn(III) in birnessites, the more Mn(III) newly formed from the transformation of Mn(IV) is complexed out from the minerals, and the greater amplitude in the decrease of Cr(III) oxidation rate. Thus the newly formed Mn(III) is highly active and possesses fast rate of electron transfer, however the rate of electron transfer in the transformation process of Mn(IV) --> Mn(III) is relatively slow. It could be deduced that the controlling step of initial oxidation rate of Cr(III) with birnessites may be the electron transfer process of Mn(IV) --> Mn(III).

[Relation between average oxidation state of Mn of birnessite and the amount of Pb2+ adsorbed].

Vacant sites in Mn oxides, commonly occur in soils, play an important role in their heavy metal adsorption behavior. The dependence of Pb2+ adsorption capacity for the synthesized birnessites and their d110-interplanar spacing on the respective Mn average oxidation state (AOS), and the relationship between Pb2+ adsorption and the Mn2+, H+, K+ released during adsorption were investigated. The results show that Mn AOS of birnessites apparently reflects their amount of vacant sites which largely account for the Pb2+ adsorption. Significant positive correlation between Pb2+ adsorption capacity and the Mn AOS of corresponding birnessites (r = 0.9779 > 0.6614, n = 14, alpha = 0.01), negative correlation between d110 spacing and the Mn AOS (r = -0.9035 < -0.6614, n = 14, alpha = 0.01), and significant positive correlation between Pb2+ adsorption and the Mn2+, H+, K+ released during adsorption(r = 0.9962 > 0.6614, n = 14, alpha = 0.01) are found. The vacant sites amount increases with Mn AOS for birnessites, which causes the increase of Pb2+ adsorption. Therefore, the Pb2+ adsorption capacity of birnessite is largely determined by the amount of vacant sites, from which Mn2+, H+, and K+ released during adsorption are mostly derived.